226 THE RIDDLE OF THE UNIVERSE. 



errors need no further refutation to-day, for experience 

 has never yet discovered for us a single immaterial 

 substance, a single force which is not dependent on 

 matter, or a single form of energy which is not exerted 

 by material movement, whether it be of mass, or of 

 ether, or of both. Even the most elaborate and most 

 perfect forms of energy that we know — the psychic 

 life of the higher animals, the thought and reason of 

 man — depend on material processes, or changes in the 

 neuroplasm of the ganglionic cells ; they are incon- 

 ceivable apart from such modifications. I have already 

 shown (chap, xi.) that the physiological hypothesis of 

 a special, immaterial " soul-substance " is untenable. 



The study of ponderable matter is primarily the 

 concern of chemistry. Few are ignorant of the 

 astonishing theoretical progress which this science 

 has made in the course of the century and the 

 immense practical influence it has had on every 

 aspect of modern life. We shall confine ourselves 

 here to a few remarks on the more important 

 questions which concern the nature of ponderable 

 matter. It is well known that analytical chemistry 

 has succeeded in resolving the immense variety of 

 bodies in nature into a small number of simple 

 elements — that is, simple bodies which are incapable 

 of further analysis. The number of these elements 

 is about seventy. Only fourteen of them are widely 

 distributed on the earth and of much practical 

 importance; the majority are rare elements (prin- 

 cipally metals) of little practical moment. The 

 affinity of these groups of elements, and the remark- 

 able proportions of their atomic weights, which 

 Lothar Meyer and Mendelejeff have proved in their 

 Periodic System of the Elements, make it extremely 



